DNA / Forensic Science Solutions

Steve Mercer is an Associate Member of the American Academy of Forensic Sciences

Challenges to the use of DNA/forensic science evidence in criminal trials, appeals, and post-conviction proceedings is a core practice area at RaquinMercer.  Steve Mercer’s litigation experience in private practice and as the Chief Attorney for the Forensics Division of the Maryland Public Defender has focused on DNA/forensic science. Now he has partnered with Isabelle Raquin to provide DNA/forensic science solutions for defense attorneys.

Steve and Isabelle know that defense attorneys must aggressively challenge the admissibility and weight of DNA/forensic science that is error prone, premised on highly subjective judgments, and vulnerable to bias and exaggerated claims of uniqueness. Over the past decade, the scientific community has produced two comprehensive and sharply critical assessments of the state of forensic science in the United States.  How should defense attorneys respond?  What new pathways of litigation will leverage this substantial increase in the scientific knowledge base concerning errors in DNA/forensic science?  Will the litigation avenue you select succeed in your case?

One answer is certain:  invoking the NAS or PCAST reports—which  contain  authoritative criticism of the reliability of a wide range of DNA/forensic science disciplines—will not compel the exclusion in a criminal case  of a  method prone to error. To mount an effective challenge, the defense ordinarily must identify actual problems with the method as applied to the evidence tested in a particular case. This practical reality means defense attorneys must aggressively pursue complete discovery.  Yet formulating a comprehensive discovery plan is a substantial undertaking itself that requires, at a minimum:

  • Expertise with the discipline at issue; the analyst(s) and laboratory testing the evidence;
  • Knowledge of the expected documentation associated with an analysis and interpretation;
  • Recognition of the customary and ordinary language and assumptions used in reports verse unusual terms, caveats, or unreasonable assumptions;
  • Awareness of the gaps in a laboratory’s standard protocols for documenting the results of bench work that can obscure anomalies in data collection procedures;
  • Knowledge of the limitations of information contained in pass/fail reports of proficiency reports and where to find administrative and technical errors in these tests;
  • Knowledge of how accrediting and licensing bodies conduct audits and laboratory’s manage other quality assurance measures that can include documentation of errors, anomalies, or issues in the laboratory;
  • Experience interviewing analysts and onsite reviews of case related documentation.

This is a steep learning curve, but obtaining full discovery increases the likelihood that actual problems with the application of a method at issue to the evidence in your case will be identified. Further, without full discovery, the defense cannot evaluate the need or fit for a subject matter expert. An essential part of a successful challenge is litigating discovery. Only then can problems be identified and litigation solutions developed.

Contact RaquinMercer today for information on consulting with Steve and Isabelle about discovering problems with DNA/forensic science in your case and developing solutions as robust as your need.

DNA/Biological Evidence

The most common types of biological evidence include blood, saliva, skin cells / perspiration (“touch DNA”) and semen. Typically, the dual aim of the testing is to indicate the type of biological evidence and provide sufficient samples of biological evidence to allow DNA profiling. DNA is touted as the “gold standard” but not all DNA is the same.  The relentless demand for DNA evidence in criminal prosecutions and swifter, more sensitive testing methods create opportunities for error in source attribution and the identification of bodily fluids.

Weapons Evidence

Weapons evidence consists of firearms (handguns / rifles / shotguns), ammunition (spent casings, fired projectiles, bullet fragments, and unfired bullets), gunshot residue (GSR) tests, and knives.  The discipline of firearm/toolmark comparisons and related gunshot residue testing were created by law enforcement—not the scientific community.  Like other methods developed to produce evidence for use in criminal prosecutions, the discipline relies heavily on an examiner’s subjective judgment that is formed using a methodology which lacks foundational reliability.

Fingerprint Evidence

Fingerprint evidence consists of comparisons between “10-prints” (fingerprints collected from a known person) and latent prints (only partial prints of one or more fingers collected from evidence associated with a crime).  Similar to other pattern impression disciplines created by and for law enforcement, there are gaps in the methodology when applied to complex real-world conditions (including partial/degraded latent prints and cues from case related communications and automated identification systems) that can bias an examiner’s subjective judgment.

Drug Evidence

Drug evidence includes drugs (PCP, heroin, marijuana, cocaine, methamphetamine, and others), and drug paraphernalia (pipes, spoons, papers) found at a scene, on a person, or used in a transaction.  The scientific community has demonstrated the validity of certain drug testing methods, such as gas chromatography/mass spectrometry (GC/MS) or thin-layer chromatography (TLC) when used in accordance with validated protocols.  The existence of reliable protocols does not however, mean the protocols were actually followed by a law enforcement laboratory in real-world conditions (high throughput of samples, poor oversight/review, training, pressure from trial deadlines) to real-world evidence.  Testing of residue and synthetics are particular areas of concern.

Pattern Impressions Evidence

Pattern impressions evidence includes bitemark impressions / comparisons, shoeprint impressions, tire tracks, and tool marks.  Pattern impression evidence is highly prone to false positives, misidentifications, and exaggerated claims of weight.  The scientific community has generally accepted that bitemark impression evidence is unreliable, but some courts continue to admit it.

Trace Evidence

Trace evidence describes the category of evidence that includes small, possibly microscopic, material. It covers a wide variety of evidence, but most typically involves hair and fibers (natural and synthetic).  A microscopic examination for optical similarities between question hairs or fibers and known hairs or fibers is a methodology unique to law enforcement, and the process is highly vulnerable to examiner bias, error, and exaggerated statements about weight and uniqueness. Gas chromatography/mass spectrometry (GC/MS) has long been the accepted method for qualitative analysis of synthetic fibers (typically carpet fibers) but the collection and analysis of trace evidence and the reporting of results can be susceptible to error due to contamination, transfer, and bias, i.e., cherry-picking consistent data while ignoring inconsistent data.

Digital Evidence

Electronic and printed data include documents and electronics (computers, cell phones, GPS), as well as video and audio recordings and other forms of surveillance (facial recognition).  Digital evidence is highly vulnerable to errors because the objective of a forensic analysis of digital evidence is not a purely qualitative undertaking.  The purpose is to obtain evidence that implies the actions of a person associated with the data.  Examiners may not account for systemic error in data collection. This problem is compounded by tunnel vision and a failure to consider alternative explanations for the data.

Medical and Pathology Evidence

Medical and Pathology evidence include cause and manner of death, nature and extent of injuries, and accidental / non-accidental causes of trauma.  Because the cause and manner of death or injury are inherently opinions, subjective judgment is required to formulate these legally non-binding conclusions.  Often the circumstances of a death or injury, in particular the history provided by a caregiver, inform the degree of certainty for a doctor’s judgment—rather than empirical data establishing the foundational validity of an underlying medical or scientific phenomenon.

Forensic Science Consulting FAQ’s

Can I challenge “touch DNA” more so than plain-old DNA testing?

Yes. “Touch DNA” typically involves very sensitive testing methods that increases the uncertainty of the reported results due to possible contamination and stochastic effects inherent at very low levels of DNA. This greater uncertainty often requires an analyst to exercise judgment and discretion.  Because “success” for a forensic scientist is too-often defined by whether the evidence helps the prosecution secure a conviction, the accuracy of the process must be closely scrutinized. Contact RaquinMercer to consult with Steve about a challenge to touch DNA.

Can I challenge a mixture of DNA more so than plain-old DNA testing?

Yes. A mixed DNA profile often involves a complex set of data with a higher degree of uncertainty than plain-old DNA testing.  Often, an analyst will base her entire conclusion on unstated, subjective assumptions about the number of contributors and the identity of some of the contributors based on a factual scenario provided by the police. Contact RaquinMercer to consult with Steve about a challenge to the admissibility of a complex mixture of DNA.

Can the defense conduct DNA testing of evidence?

Ordinarily, yes. In general, a defendant has the right to inspect and test evidence in the possession of the police before trial. There are important tactical issues to consider however. Post-conviction DNA testing is more restricted. Ordinarily it is governed by the applicable state or federal law.  For example, Maryland provides a limited statutory right to test evidence post-conviction for qualifying convictions. Contact RaquinMercer to consult with Steve about possible DNA testing of evidence.

Can I challenge DNA test results?

DNA is often the most powerful evidence in a case. It may be a question of “what” it is, or “how it got there.” To develope effective tactics for a particular case, complete discovery is needed to identify any potential problem or limitation of the reported results. Then solutions for your case can be developed. Contact RaquinMercer to consult with Steve about the DNA evidence in your case.